Interacción entre la función reproductiva y metabólica: caracterización del papel de factores neuroendocrinos y el sensor energético, proteína quinasa activada por AMP (AMPK)

La reproducción es un proceso costoso en términos de consumo energético que, si bien es esencial para la supervivencia de las especies, es prescindible a nivel individual. Por lo tanto, la maduración y la función del eje reproductor están estrechamente conectadas con el estado energético del organismo y se encuentran bajo el control de una red sofisticada de factores reguladores, donde señales neuronales, hormonales y ambientales cooperan para garantizar su correcta maduración, durante distintas etapas del desarrollo, y su mantenimiento funcional en la edad adulta, siempre que las condiciones nutricionales y metabólicas sean adecuadas. El éxito de este proceso está dirigido por la acción integrada de las señales del denominado eje Hipotálamo- Hipófiso-Gonadal (HHG), en el que las neuronas GnRH ocupan una posición destacada controlando la reproducción y su modulación mediante señales metabólicas (1, 2). Las neuronas Kiss1, por su parte, son elementos clave en el control de la reproducción, ya que regulan la liberación de GnRH y, por ende, de las gonadotropinas, y además son capaces de transmitir información metabólica a las neuronas GnRH, estimulando o inhibiendo su síntesis (3). En este contexto, en las últimas décadas se han descubierto un gran número de señales de origen central y periférico, responsables de la adecuación de la función reproductora a la disponibilidad de recursos energéticos del organismo. En líneas generales, puede asumirse que las señales de suficiencia energética (anorexigénicas) estimulan la puesta en marcha y funcionamiento del eje reproductor, mientras que las señales que informan de la escasez de recursos energéticos (orexigénicas) inhiben el funcionamiento del eje reproductor. De esta forma, se han desarrollado mecanismos sofisticados durante la evolución para permitir una inhibición específica del eje reproductor en condiciones energéticas desfavorables (3). Dichas condiciones metabólicas adversas pueden concurrir en situaciones tanto de déficit como de exceso de los depósitos energéticos del organismo. Así, tanto en países desarrollados como en países en vías de desarrollo, la prevalencia de la obesidad y las patologías asociadas está aumentando a un ritmo de proporciones epidémicas. Las razones se deben a una combinación entre la predisposición genética y los factores sociales y ambientales, que conducen a un desequilibrio en el balance energético, y se asocia con la hipertensión, la diabetes tipo 2, el hígado graso y una variedad de trastornos conocidos como síndrome metabólico. De otra parte, diversas condiciones, algunas de prevalencia creciente, se asocian a un déficit energético severo, tales como la anorexia nerviosa, la caquexia tumoral y otras patologías consuntivas, o incluso programas de entrenamiento físico intensivo, tales como los propios de deportistas profesionales. En unas y otras condiciones, dependiendo del momento en el que concurran, tanto la pubertad como la fertilidad y la función gonadal pueden verse severamente afectadas (4). A su vez, la propia función gonadal puede influenciar el estado metabólico del organismo, de suerte que las secreciones gonadales, como los andrógenos y los estrógenos, son potentes moduladores de la homeostasis metabólica y del peso corporal. Por todo ello, diversas evidencias experimentales apuntan que no sólo cambios nutricionales y otras situaciones de estrés metabólico, sino también niveles inapropiados de hormonas sexuales en determinados periodos del desarrollo, pueden contribuir a desencadenar alteraciones metabólicas y a modificar de manera permanente la función reproductora (5, 6). Sin embargo, los mecanismos neurohormonales que subyacen a esta interacción bidireccional entre el metabolismo y el eje reproductor permanecen aún en gran medida desconocidos. Por otro lado, además de distintas señales centrales y periféricas, evidencias recientes sugieren la participación de sensores energéticos celulares en el control metabólico de la función reproductora. Entre ellos, destaca la proteína quinasa activada por AMP, denominada AMPK, un sensor energético clave que se activa en condiciones de déficit energético y está implicado en la homeostasis energética del organismo, principalmente a través de la regulación de la ingesta y el gasto energético, ejerciendo su acción en los núcleos hipotalámicos, arcuato (ARC) y ventromedial (VMN), respectivamente (7). Además, estudios recientes han sugerido que AMPK opera como una vía clave que informa y modula al eje HHG en situaciones de insuficiencia energética, si bien las evidencias que apoyan dicho papel son aún fragmentarias y no concluyentes, sin una caracterización clara del papel de la señalización de AMPK en poblaciones neuronales clave para el control metabólico de la función reproductora (1). En suma, aun cuando es evidente que existe un claro acoplamiento entre el estado energético y metabólico del organismo, y la maduración y función del eje reproductor, aún no se conocen en profundidad las redes neuronales y las bases hormonales y moleculares de los mecanismos que intervienen en este fenómeno fisiológico. Todo ello hace necesario un mejor conocimiento de las complejas interacciones bidireccionales entre el estado metabólico y la función reproductiva, las bases neuroendocrinas de dichas interacciones, y los mecanismos moleculares que conectan ambos sistemas corporales relevantes. Teniendo en cuenta lo expuesto previamente, el objetivo general de esta Tesis Doctoral ha sido profundizar en la caracterización de las interacciones dinámicas entre el estado metabólico del organismo y aspectos clave de la maduración y la función reproductora. En este contexto, en esta Tesis se ha prestado especial atención a la definición del impacto de cambios en la función gonadal y la exposición a factores obesogénicos sobre el perfil endocrino-metabólico en la edad adulta y a la evaluación del posible papel del sensor energético celular, AMPK, actuando en las neuronas GnRH y Kiss1, en el control metabólico de la función reproductora

Effect of Epas1 and Pcx inactivation in pancreatic β-cell formation and function.

According to the consensus model for GSIS (Glucose-Stimulated Insulin Secretion), glucose is rapidly metabolized and coupled to insulin secretion involving a substantial number of cofactors and metabolites intermediates such as ATP, NADPH and citrate, among many others (1). In particular, pyruvate carboxylase (PC) is a fundamental enzyme in redox cycling between NADH and NADPH and also participates in an intricate process known as “pyruvate cycling” which allows the anaplerotic entry of pyruvate in the krebs cycle (2).Pancreatic β-cells express abnormally high levels of pyruvate carboxylase (PC) and insignificant levels of phosphoenolpyruvate carboxylase, the enzyme necessary for gluconeogenesis. This implies that PC must play a different role in β-cells, such as insulin secretion, which is required for the "metabolic switch" from glycolytic to aerobic metabolism during β-cell maturation. It is also known that pyruvate carboxylase activity is elevated in mature β-cells but diminished under diabetic conditions. Recent studies have revealed that the Hypoxia Inducible factor (HIF) pathway plays an important role of in β-cell function (cita algun articulo nuestro). Both overexpression and inactivation of HIF-1α in β cells cause defects in insulin secretion. However, the role of HIF-2α in β-cell formation and function has been largely ignored despite been reported to be activated during diabetic conditions.In this project, we hypothesize that HIF-2α and pyruvate carboxylase activity during late pancreatic HIF-2α formation is critical for the metabolic switch that ocurrs in β-cell during early postnatal development and thus for proper β-cell function.In this study, we will analyze the expression of Epas1 (the gene encoding HIF-2α and Pcx) at different prenatal and postnatal stages by mRNA TaqMan essay. Using Cre/lox technology in mice, we will inactivate Epas1 and Pcx specifically in β-cells. Immunofluorescence and immunohistochemical assays will be carried out to determine specific markers of cell identity, vascularization, proliferation, and polarity in pancreatic tissue of Epas1- and Pcx-deficient mice. Finally, we will also evaluate the in vivo behavior of pancreatic β-cells in transgenic mice through glucose and insulin tolerance assays (GTT and ITT). This will help us understand the relationship between HIF-2 and PC activity and β-cell development and function, as well as whether HIF-2 and PC activity play a role in β-cell failure during diabetes

Molecular analysis of prolactinoma formation in Pten-deficient mice.

Pituitary tumors are abnormal masses developed in the pituitary gland. Although they are generally benign, between 40-50% of pituitary adenomas cannot be removed by surgery alone due to local invasion. Moreover, they are associated with hormonal dysregulation. Prolactinoma is the most common type (50-60%), followed by somatotropic cell adenoma (10-15%), corticotropic cell adenoma (5-10%) and finally thyrotropinoma (less than 1%) (Cano González et al., 2015).Previous descriptive studies have suggested a possible role for the PI3K/AKT/mTOR signaling pathway in the formation of pituitary adenomas. In this study, we used genetic mouse models to assess the oncogenic capacity of this signaling pathway in the pituitary. For this purpose, conditional knockout mice have been generated in which the Pten gene is inactivated specially in the pituitary, indirectly causing the AKT overexpression. To accomplish this, a HesX1-Cre mouse line, whose expression is controlled by a pituitary-specific promoter and which is present in very early stages of embryonic development (Rizzoti, 2015) were crossed with mouse lines in which the Pten gene is floxed by two LoxP sequences.We have analyzed the pituitary in Pten-deficient mice at three different ages: 12, 6 and 1 month of age, comparing genotype and sex. At young ages, Pten-deficient mice show pituitary hyperplasia. After 12 months of age, Pten-deficient mice develop pituitary tumors. However, this is only observed in mutant female mice, whereas male mice simply display pituitary hyperplasia. Data from immunohistochesmistry, immunofluorescence, and blood hormones show that Pten-deficient mice developed prolactinomas. These tumors show high rates of cell proliferation as well as alterations in the expression levels of several cell cycle inhibitors

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Direct Actions of Kisspeptins on GnRH Neurons Permit Attainment of Fertility but are Insufficient to Fully Preserve Gonadotropic Axis Activity.

Kisspeptins, ligands of the receptor, Gpr54, are potent stimulators of puberty and fertility. Yet, whether direct kisspeptin actions on GnRH neurons are sufficient for the whole repertoire of their reproductive effects remains debatable. To dissect out direct vs. indirect effects of kisspeptins on GnRH neurons in vivo, we report herein the detailed reproductive/gonadotropic characterization of a Gpr54 null mouse line with selective re-introduction of Gpr54 expression only in GnRH cells (Gpr54(-/-)Tg; rescued). Despite preserved fertility, adult rescued mice displayed abnormalities in gonadal microstructure, with signs of precocious ageing in females and elevated LH levels with normal-to-low testosterone secretion in males. Gpr54(-/-)Tg rescued mice showed also altered gonadotropin responses to negative feedback withdrawal, while luteinizing hormone responses to various gonadotropic regulators were variably affected, with partially blunted relative (but not absolute) responses to kisspeptin-10, NMDA and the agonist of tachykinin receptors, NK2R. Our data confirm that direct effects of kisspeptins on GnRH cells are sufficient to attain fertility. Yet, such direct actions appear to be insufficient to completely preserve proper functionality of gonadotropic axis, suggesting a role of kisspeptin signaling outside GnRH cells

Reduction of cardiac imaging tests during the COVID-19 pandemic: The case of Italy. Findings from the IAEA Non-invasive Cardiology Protocol Survey on COVID-19 (INCAPS COVID)

Background: In early 2020, COVID-19 massively hit Italy, earlier and harder than any other European country. This caused a series of strict containment measures, aimed at blocking the spread of the pandemic. Healthcare delivery was also affected when resources were diverted towards care of COVID-19 patients, including intensive care wards. Aim of the study: The aim is assessing the impact of COVID-19 on cardiac imaging in Italy, compare to the Rest of Europe (RoE) and the World (RoW). Methods: A global survey was conducted in May–June 2020 worldwide, through a questionnaire distributed online. The survey covered three periods: March and April 2020, and March 2019. Data from 52 Italian centres, a subset of the 909 participating centres from 108 countries, were analyzed. Results: In Italy, volumes decreased by 67% in March 2020, compared to March 2019, as opposed to a significantly lower decrease (p &lt; 0.001) in RoE and RoW (41% and 40%, respectively). A further decrease from March 2020 to April 2020 summed up to 76% for the North, 77% for the Centre and 86% for the South. When compared to the RoE and RoW, this further decrease from March 2020 to April 2020 in Italy was significantly less (p = 0.005), most likely reflecting the earlier effects of the containment measures in Italy, taken earlier than anywhere else in the West. Conclusions: The COVID-19 pandemic massively hit Italy and caused a disruption of healthcare services, including cardiac imaging studies. This raises concern about the medium- and long-term consequences for the high number of patients who were denied timely diagnoses and the subsequent lifesaving therapies and procedures

International Impact of COVID-19 on the Diagnosis of Heart Disease

Background: The coronavirus disease 2019 (COVID-19) pandemic has adversely affected diagnosis and treatment of noncommunicable diseases. Its effects on delivery of diagnostic care for cardiovascular disease, which remains the leading cause of death worldwide, have not been quantified. Objectives: The study sought to assess COVID-19's impact on global cardiovascular diagnostic procedural volumes and safety practices. Methods: The International Atomic Energy Agency conducted a worldwide survey assessing alterations in cardiovascular procedure volumes and safety practices resulting from COVID-19. Noninvasive and invasive cardiac testing volumes were obtained from participating sites for March and April 2020 and compared with those from March 2019. Availability of personal protective equipment and pandemic-related testing practice changes were ascertained. Results: Surveys were submitted from 909 inpatient and outpatient centers performing cardiac diagnostic procedures, in 108 countries. Procedure volumes decreased 42% from March 2019 to March 2020, and 64% from March 2019 to April 2020. Transthoracic echocardiography decreased by 59%, transesophageal echocardiography 76%, and stress tests 78%, which varied between stress modalities. Coronary angiography (invasive or computed tomography) decreased 55% (p &lt; 0.001 for each procedure). In multivariable regression, significantly greater reduction in procedures occurred for centers in countries with lower gross domestic product. Location in a low-income and lower–middle-income country was associated with an additional 22% reduction in cardiac procedures and less availability of personal protective equipment and telehealth. Conclusions: COVID-19 was associated with a significant and abrupt reduction in cardiovascular diagnostic testing across the globe, especially affecting the world's economically challenged. Further study of cardiovascular outcomes and COVID-19–related changes in care delivery is warranted

Impact of COVID-19 on Diagnostic Cardiac Procedural Volume in Oceania: The IAEA Non-Invasive Cardiology Protocol Survey on COVID-19 (INCAPS COVID)

Objectives: The INCAPS COVID Oceania study aimed to assess the impact caused by the COVID-19 pandemic on cardiac procedure volume provided in the Oceania region. Methods: A retrospective survey was performed comparing procedure volumes within March 2019 (pre-COVID-19) with April 2020 (during first wave of COVID-19 pandemic). Sixty-three (63) health care facilities within Oceania that perform cardiac diagnostic procedures were surveyed, including a mixture of metropolitan and regional, hospital and outpatient, public and private sites, and 846 facilities outside of Oceania. The percentage change in procedure volume was measured between March 2019 and April 2020, compared by test type and by facility. Results: In Oceania, the total cardiac diagnostic procedure volume was reduced by 52.2% from March 2019 to April 2020, compared to a reduction of 75.9% seen in the rest of the world (p&lt;0.001). Within Oceania sites, this reduction varied significantly between procedure types, but not between types of health care facility. All procedure types (other than stress cardiac magnetic resonance [CMR] and positron emission tomography [PET]) saw significant reductions in volume over this time period (p&lt;0.001). In Oceania, transthoracic echocardiography (TTE) decreased by 51.6%, transoesophageal echocardiography (TOE) by 74.0%, and stress tests by 65% overall, which was more pronounced for stress electrocardiograph (ECG) (81.8%) and stress echocardiography (76.7%) compared to stress single-photon emission computerised tomography (SPECT) (44.3%). Invasive coronary angiography decreased by 36.7% in Oceania. Conclusion: A significant reduction in cardiac diagnostic procedure volume was seen across all facility types in Oceania and was likely a function of recommendations from cardiac societies and directives from government to minimise spread of COVID-19 amongst patients and staff. Longer term evaluation is important to assess for negative patient outcomes which may relate to deferral of usual models of care within cardiology